Interpretive Summary: Large amounts of nitrogen fertilizer are required for high-value crops such as potatoes. These fertilizer inputs can result in large emissions of nitrous oxide (N2O), which is a potent greenhouse gas. Specialized, coated urea fertilizer products are designed to release nitrogen slowly over the growing season, and thereby better match N supply to plant uptake. This slower release may result in lower N2O emissions. The objective of this study was to compare N2O emissions in a coarse-textured soil fertilized with 270 kg N per ha using sulfur-coated urea (KS), two different polymer-coated urea (PCU) products (ESN and KP), and conventional urea (CU). Crop yields following single, pre-plant applications of KS, ESN, and KP were no different than following multiple split CU applications. N2O emissions with CU tended to be higher than with the coated fertilizers. Of the two PCUs, the product with the greater mass of polymer coating (KP) released N more slowly and also emitted less N2O. Over both seasons, N2O emissions from KP and ESN were approximately 15% and 44% lower than CU, respectively. The amount of N2O emitted was equivalent to 0.10, 0.39, and 0.48% of the amount of fertilizer added for KP, ESN, and CU, respectively. These results show that coated urea can maintain yields while reducing N2O emissions and also reducing costs associated with split applications of conventional fertilizer. The N2O emissions results obtained in this study will assist both scientists and policy makers in improving their estimates of greenhouse gas emissions from agriculture, and in developing improved management practices for mitigating these emissions.

Technical Abstract:
Large inputs of nitrogen (N) fertilizer required for crops such as potatoes have the potential to generate soil-to-atmosphere emissions of nitrous oxide (N2O), which is a potent greenhouse gas. Coated urea fertilizer products are designed to better match N supply to plant uptake and thereby minimize N losses. The objective of this study was to compare N2O emissions and irrigated potato yields over two growing seasons in a coarse-textured soil fertilized with 270 kg N ha-1 using one sulfur-coated urea (KS), two different polymer-coated urea (PCU) products (ESN and KP), and conventional urea (CU). N release rates from the PCU prills incubated in-situ were also measured. Crop yields following single, pre-plant applications of KS, ESN, and KP were no different than following multiple split CU applications, while N2O emissions with CU tended to be higher. Of the two PCUs, the product with the greater mass of polymer coating (KP) released N more slowly and also emitted less N2O. Over both seasons, N2O emissions from KP and ESN were approximately 15% and 44% lower than CU, respectively. Emissions were 1.7 to 2.7 times higher in 2008, during which 60% of total water inputs were from rain, as compared to 2007, during which 60% of inputs were from irrigation. Fertilizer-induced emissions in 2008 amounted to 0.10, 0.39, and 0.48% with KP, ESN, and CU, respectively. These results show that coated urea can maintain yields while reducing N2O emissions and also reducing costs associated with split applications of conventional fertilizer.